1. Field of the Invention
The present invention relates to a non-aqueous pigment ink.
2. Description of the Related Art
An inkjet recording method is a printing method in which printing is conducted by spraying a liquid ink with a high degree of fluidity from very fine nozzles, and adhering that ink to a recording medium such as a sheet of plain paper. This type of method enables the printing of high-resolution, high-quality images at high speed and with minimal noise, using a comparatively inexpensive printing apparatus, and is rapidly becoming widespread.
The coloring materials for inks used in inkjet recording systems can be broadly classified into pigments and dyes. Of these, there is a growing tendency for the use of inks that use pigments as the coloring materials, as such inks exhibit the excellent levels of light resistance, weather resistance and water resistance that are required for high image quality printing.
In terms of the solvent, inks can be broadly classified into aqueous inks and non-aqueous inks. Non-aqueous inks that do not use water as the ink solvent, including solvent-based inks that use a volatile solvent as the main constituent and oil-based inks that use a non-volatile solvent as the main constituent, exhibit superior stability within the printer (such as intermittent dischargeability and discharge recovery following standing idle for a long period), cause no curling of the recorded medium and have a short ink penetration and drying time, and are therefore attracting considerable attention.
On the other hand, some inks may be prepared by combining two or more different pigments in order to achieve a printed item of a specific target color. However, in the case of a non-aqueous ink, when a color is prepared by combining pigments, achieving satisfactory color reproducibility tends to be difficult, and in particular, the saturation (or chroma) of the printed image may deteriorate. Among the various colors, achieving satisfactory color reproducibility for red colors is particularly problematic.
Further, because non-aqueous pigment inks for inkjet printing are used at comparatively low viscosities, achieving satisfactory storage stability is desirable, but when two or more pigments are mixed, achieving satisfactory storage stability for the ink tends to become more difficult.
Patent Document 1 proposes an ink comprising a pigment formed from a solid solution of C.I. Pigment Red 202 and C.I. Pigment Violet 19, wherein the primary particle size and particle size distribution of the pigment satisfy specific values. However, the Patent Document 1 describes only an aqueous medium ink, and makes no disclosure regarding non-aqueous inks.
Patent Document 1: JP 2010-202858 A
An object of the present invention is to provide a non-aqueous pigment ink that exhibits excellent color reproducibility and storage stability.